1. Field of the Invention
The present invention relates to a display including a substrate (display section) having a pixel region in which pixels are formed and a sensor region in which light receiving elements are formed. More particularly, the invention relates to a technology for enhancing the light utilization efficiency in the process in which light reflected by an object to be detected, coming into contact with or into proximity to the substrate (display section), is received by a plurality of light receiving elements.
2. Description of the Related Art
As display devices for use in mobile phones, personal digital assistants (PDA), digital still cameras, PC (personal computer) monitors, television sets, etc., there have been known liquid crystal displays, organic EL (electroluminescence) displays, displays using the electrophoretic method, and so on.
Attendant on the reductions in the thickness of displays, there has come to be a demand for a display having a multiplicity of functions, i.e., having the function of, for example, an inputting device for inputting user's instructions and the like in addition to the original function of displaying pictures, character information, etc. As a device to meet the demand, there has been known a display which detects that a user's finger or a stylus pen (so-called touch pen) has come into contact with or proximity to the display screen.
Detection of the contact can be carried out, for example, by a touch panel based on a resistance film system or a capacitance (electrostatic capacity) system. There has been known a display in which a touch panel added to the display surface side of a display panel such as a liquid crystal panel.
However, the addition of a touch panel is disadvantageous from the viewpoint of thinning the display panel, and causes a rise in cost. Especially, the resistance film system touch panel has the problem that the change in resistance value can be detected only when the screen is pressed with a certain degree of strength, which results in distortion of the display screen. Besides, the resistance film system touch panel is of one-point detection type in principle, and therefore has limited use.
In recent years, there is a movement in regard of liquid crystal displays toward the provision of a touch panel function by adopting a configuration in which photo-sensors are also formed on a transistor array substrate for controlling the driving voltage for the liquid crystal.
In relation to the display having photo-sensors on a transistor array substrate, several detecting methods have been known, for example, a method in which a finger or a stylus pen is recognized by detecting its shadow under external light, and a method in which back-light light (light from a back light) is reflected by a finger or a stylus and the reflected light is detected.
However, the method in which the finger or stylus pen is recognized by detecting its shadow under external light has the problem that the function is not attained in the dark. On the other hand, the method in which the back-light light is reflected by the finger or stylus and the reflected light is detected has the problem that detection is impossible in the case of displaying of perfect black.
Under such circumstances, Japanese Patent Laid-Open No. 2005-275644 (hereinafter referred to as Patent Document 1) proposes a liquid crystal display in which infrared light is emitted from a back light and the reflected infrared light is detected.
On the other hand, Japanese Patent Laid-Open No. 2007-241303 (hereinafter referred to as Patent Document 2) proposes a liquid crystal display in which a reflector is provided under a semiconductor layer formed from polysilicon constituting a PIN-type (p-intrinsic-n type) diode and light is reflected by the semiconductor layer so that the light absorption length is increased.